Provisional Use of CLSI-Approved Quality Control Strains for Antimicrobial Susceptibility Testing of Mycoplasma (‘Mesomycoplasma’) hyorhinis

Abstract

Antimicrobial susceptibility testing (AST) should be conducted in a standardized manner prior to the start of an antimicrobial treatment. For fastidious bacteria, such as porcine Mycoplasma (‘Mesomycoplasma’) spp., specifically M. hyorhinis, neither guidelines or standards for the performance of AST, nor quality control strains for the validation of AST results are approved by organizations like the Clinical and Laboratory Standards Institute (CLSI) or the European Committee on Antimicrobial Susceptibility Testing (EUCAST). The CLSI- and EUCAST-approved quality control strains Enterococcus faecalis ATCC 29212 and Staphylococcus aureus ATCC 29213 were chosen to validate AST by broth microdilution using modified Friis broth, developed as growth medium for porcine Mycoplasma (‘Mesomycoplasma’) spp. The antimicrobial agents doxycycline, enrofloxacin, erythromycin, florfenicol, gentamicin, marbofloxacin, tetracycline, tiamulin, tilmicosin, tulathromycin, and tylosin were examined using customized SensititreTM microtiter plates. Minimal inhibitory concentrations, determined after 24, 48, and 72 h, were mostly within the CLSI-approved quality control ranges for defined antimicrobial agents. We propose the use of the combination of E. faecalis ATCC 29212 and S. aureus ATCC 29213 as surrogate quality control strains for the validation of future AST results obtained for M. hyorhinis by broth microdilution using modified Friis broth.

Conventional methods and future trends in antimicrobial susceptibility testing

“…Staphylococcus aureus ( S. aureus ) ATCC® 25923, Escherichia coli ( E . coli ) ATCC®25922, and Pseudomonas aeruginosa ( P. aeruginosa ) ATCC®27853 are frequently used ATCC strains in the clinical microbiology laboratories ( Nassar et al, 2019 , Käbisch et al, 2021 ).…”

Towards a Standardized Antimicrobial Susceptibility Testing Method for Mycoplasma hyorhinis

“…For the purpose of broth media evaluation, the type strain of M. hyopneumoniae NCTC 10110 (ATCC 25934) was procured at the National Collection of Type Cultures (NCTC, Salisbury, UK). The strains Enterococcus faecalis DSM 2570 (ATCC 29212) and Staphylococcus aureus DSM 2569 (ATCC 29213) were obtained from the DSMZ as well and used as quality control strains in antimicrobial susceptibility testing, as previously described [21]. A total of nine field isolates of M. hyorhinis were derived from clinical cases (nasal cavity, lung, broncho-alveolar lavage fluid, joint, and serosa) collected over an 18-year period (2003-2021) in Austria and Germany (Table 1).…”

“…The modified Friis broth was used as a culture and test medium for the broth microdilution method, as previously described [21]. The stability of the broth as a test medium was evaluated by batch testing of individual substances.…”

“…The provisional use of the quality control strains E. faecalis ATCC 29212 and S. aureus ATCC 29213 for validation purposes of the establishment of the AST method was previously described in detail [21]. CLSI standards were applied, except for using modified Friis broth instead of cation-adjusted Mueller Hinton broth and extending the incubation and reading times due to prolonged incubation times of the M. hyorhinis inoculated microtiter plates.…”

Evaluation of a Method for Standardized Antimicrobial Susceptibility Testing with Mycoplasma hyorhinis Field Isolates

“…We have recently published a broth microdilution method suitable for standardization including quality control (QC) strains for AST of M. hyorhinis [35,36]. In this study, we further evaluated this methodology by applying it to a variety of M. hyorhinis field isolates.…”